JP2006336591A - Abnormality determination device for oxygen sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality detection device for an oxygen sensor suitably detecting abnormality of an oxygen sensor. <P>SOLUTION: The abnormality detection device 100 for an oxygen sensor 10 is disposed between the air and exhaust gas emitted when an internal combustion engine burns air-fuel mixture with a predetermined air-fuel ratio, and is provided with a detection element 1 generating an electromotive force depending on oxygen partial pressure difference between the air and the exhaust gas. The abnormality detection device includes a first control means and a diagnosing means. The first control means executes a first control wherein, when an output signal 11a is below a first threshold value 12, the first control means changes the air-fuel ratio 14 to be a first target value 15 richer than a theoretical air fuel ratio, and when the output signal 11a exceeds a second threshold value 13, the first control means changes the air-fuel ratio 14 to be a second target value 16 leaner than the theoretical air fuel ratio. The diagnosing means performs a control for diagnosing presence or absence of an abnormality of the oxygen sensor 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an abnormality detection device for an oxygen sensor.

  An internal combustion engine such as a gasoline engine or a diesel engine is provided with an exhaust gas purification system in order to remove harmful components contained in the exhaust gas. In order for this exhaust gas purification system to function effectively, it is important to strictly control the mixing ratio of the air (air) combusted in the internal combustion engine and the fuel, that is, the air-fuel ratio. Therefore, an oxygen sensor that detects the oxygen partial pressure of the exhaust gas is installed in the exhaust passage of the internal combustion engine, and feedback control is performed so that an ideal air-fuel ratio (stoichiometric) can be obtained.

FIG. 10A is a diagram showing a detection element portion in a general oxygen sensor. The oxygen sensor 100 includes a cylindrical detection element unit 101 disposed so as to protrude into the exhaust passage 120. The detection element unit 101 is formed so that air (air) Air is introduced to the inner surface side, and the exhaust gas EG that has passed through the sensor cover 102 contacts the outer surface side. FIG. 10B is a diagram showing a cross-sectional structure of the detection element portion 101 in the CR in FIG. As shown in FIG. 10B, the detection element portion 101 has a structure in which a solid electrolyte 107 is interposed and an atmospheric electrode 105 is coated on the inner side and an exhaust electrode 106 is coated on the outer side. The solid electrolyte 107 is formed of a substance that can move inside the state in which oxygen (O ₂ ) is ionized (O ²⁻ ), such as zirconia.

There is an oxygen partial pressure difference between the atmosphere and exhaust gas, and generally the oxygen partial pressure on the atmosphere side is high. As a result, oxygen is ionized and moves from the atmosphere side to the exhaust gas side via the solid electrolyte 107 so that the oxygen partial pressure difference between the inner atmosphere and the outer exhaust gas is reduced in the oxygen sensor 100. As shown in FIG. 10B, oxygen molecules receive tetravalent electrons (e ⁻ ) in the process of ionization, and emit tetravalent electrons in the process of returning from the ionized state to the molecule. In response to such oxygen movement, electrons move in the electrodes 105 and 106 on the inner and outer surfaces of the detection element unit 101, and an electromotive force is generated in the detection element unit 101. As described above, the oxygen sensor 100 outputs a voltage corresponding to the oxygen partial pressure of the atmosphere and the exhaust gas, and thus has been conventionally used as an air-fuel ratio control sensor.

  However, as shown in FIG. 10 (A), an abnormality such as a crack (hereinafter simply referred to as a crack CK) may occur in the detection element portion 101 of the oxygen sensor 100 that causes the atmosphere side and the exhaust side to communicate with each other. . If the detection element unit 101 has a crack CK, the exhaust gas EG may enter the detection element unit 101 (at the atmospheric electrode 105 side). If such a situation occurs, the oxygen sensor 100 will not function correctly.

  Therefore, Patent Document 1 proposes an abnormality diagnosis device that determines the presence or absence of a detection element defect (a crack in the detection element portion) of an oxygen sensor. This diagnosis device diagnoses the abnormality of the oxygen sensor by determining the presence or absence of cracks in the detection element portion based on the output distribution of the detection signal of the oxygen sensor. The technique proposed in Patent Document 1 focuses on the fact that the output pattern of the oxygen sensor when a crack occurs in the detection element unit is different from that in the normal state, and compares the output distribution of detection signals to detect cracks in the detection element unit. Whether or not there is.

JP 2003-14683 A

  The abnormality diagnosis device of Patent Document 1 distinguishes from the normal state by utilizing the fact that the air-fuel ratio tends to be biased to a lower voltage range indicating that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio when the detection element portion has a crack. It is carried out. However, depending on the operation state of the internal combustion engine, there is a situation where the operation is biased toward a lean atmosphere (a state where the ratio of the lean operation time is large with respect to a predetermined time). In such a case, it is difficult to determine the presence or absence of cracks in the detection element unit with the apparatus of Patent Document 1.

  The present invention has been made in view of the above problems, and an object thereof is to provide an abnormality detection device for an oxygen sensor that more suitably detects an abnormality.

  In order to solve the above-mentioned problem, the present invention is arranged between a first gas and a second gas, and generates an electromotive force according to a difference in oxygen partial pressure between the first gas and the second gas. An oxygen sensor abnormality detection device including a detection element that is generated, wherein the second gas is an exhaust gas exhausted when an internal combustion engine burns an air-fuel mixture at a predetermined air-fuel ratio, and the oxygen sensor A diagnosis unit that executes control for diagnosing whether or not there is an abnormality, and a threshold value that is set for the output signal of the oxygen sensor before the diagnosis unit performs control that diagnoses whether or not the oxygen sensor is abnormal And a first control means for executing a first control for changing the air-fuel ratio of the air-fuel mixture to be leaner or richer than the stoichiometric air-fuel ratio based on a first output signal of the oxygen sensor when passing through It is characterized by that. According to the present invention, periodic pulsations, that is, pressure fluctuations, can be generated in the exhaust gas exhausted from the internal combustion engine. As a result, for example, when an oxygen sensor is disposed in an exhaust passage connected to the internal combustion engine, if there is a defect in the detection element, the exhaust gas can surely enter the detection element through the defect. That is, if the first control is executed before the oxygen sensor abnormality diagnosis is executed, the oxygen sensor abnormality diagnosis can be suitably executed. Further, according to the present invention, control is performed so as to change the air-fuel ratio based on the first output signal of the oxygen sensor, so that the first control can be executed without requiring a special additional circuit.

  Further, according to the present invention, the diagnosis unit diagnoses the presence or absence of an abnormality of the oxygen sensor based on the second output signal of the oxygen sensor when the first control unit executes the first control. Control may be performed. According to the present invention, unlike the case where the output signal of the oxygen sensor is detected alone at a certain moment, for example, the second output signal of the oxygen sensor when the first control is executed is detected. Changes in the output signal can be captured. If abnormality diagnosis is executed based on this output signal, abnormality of the oxygen sensor can be suitably detected.

  In the present invention, the diagnosis unit may execute control for diagnosing that there is an abnormality by detecting that the peak value of the second output signal has changed a predetermined value or more continuously for a predetermined number of times. .

  In the present invention, the diagnosis unit may perform control for diagnosing that there is an abnormality by detecting that the amplitude of the second output signal has changed a predetermined value or more continuously for a predetermined number of times.

  In the present invention, the diagnosis unit may execute control for diagnosing that there is an abnormality by detecting that the peak value of the second output signal has become zero continuously for a predetermined number of times.

  Further, according to the present invention, the diagnostic means reverses the oxygen concentration in the oxygen sensor in which the peak value of the second output signal is continuous for a predetermined number of times and the oxygen concentration of the gas contacting the inner and outer surfaces of the detection element is normal. It is also possible to execute control for diagnosing that there is an abnormality by detecting that the output signal indicates that there is an abnormality.

  Further, the present invention provides the first control when the diagnostic means stops when the first control is stopped because the second output signal of the oxygen sensor does not pass the threshold value. It may be possible to execute a control for diagnosing that there is an abnormality by detecting that the stop has occurred within a predetermined time.

  Further, according to the present invention, the diagnosis unit detects that the number of times the first control unit has changed the air-fuel ratio to rich or lean is not more than a predetermined number within a predetermined time, and diagnoses that there is an abnormality. Control may be executed.

  Further, the present invention provides a second control for performing fuel cut in the internal combustion engine, a third control for changing the air-fuel ratio to be leaner than a stoichiometric air-fuel ratio, and before executing the second control, or Before executing the third control, the second control means executes at least one of the fourth control for changing the air-fuel ratio to be richer than the stoichiometric air-fuel ratio, and the second control The apparatus further includes a diagnosis unit that executes control for diagnosing whether or not the oxygen sensor is abnormal based on an output signal of the oxygen sensor after the unit executes at least one of the second to fourth controls. Good. According to the present invention, when the second control unit executes at least one of the second to fourth controls, the oxygen concentration of the gas contacting the outer surface of the detection element can be increased. As a result, when exhaust gas penetrates into the detection element of the oxygen sensor through a defect, the oxygen partial pressure difference of the gas in contact with the inner and outer surfaces of the detection element is reversed from the oxygen partial pressure difference of a normal sensor. Can do. Here, when the second, third, or fourth control is executed, the exhaust gas that has entered from the defect of the detection element may flow out, so that an abnormality that is executed after that is compared with the time when the first control is executed. It can be said that the detection accuracy of diagnosis is lowered. However, according to the present invention, the first control and the second, third, or fourth control can be used properly according to the situation before executing the abnormality diagnosis, so the first control is executed. It is possible to reduce emissions contained in exhaust gas that is generated more frequently. The output signal detected for diagnosis after executing at least one of the second to fourth controls may be, for example, the output signal of the oxygen sensor detected alone at a certain moment.

  Further, according to the present invention, in the exhaust passage connected to the internal combustion engine, the oxygen sensor is disposed on the downstream side of the catalyst provided in the exhaust passage, and when the catalyst is deteriorated, the first control means is the first control means. Control may be performed.

  For example, when the maximum oxygen storage capacity indicating the ability of the catalyst to store oxygen is measured over time, and the maximum oxygen storage capacity is lower than a predetermined value, that is, when the catalyst is deteriorated, the inner and outer surfaces of the detection element Since the difference in oxygen concentration of the gas in contact with the gas becomes smaller than that before the catalyst is deteriorated, it is difficult to detect abnormality of the oxygen sensor. According to the present invention, when it is determined that the catalyst has deteriorated, the first control with higher detection accuracy can be executed as compared with the second to fourth controls. Further, when the catalyst is not deteriorated, it is possible to perform abnormality diagnosis of the oxygen sensor by the second control means, so that the emission contained in the exhaust gas can be reduced as in the case described above.

  Further, in the present invention, when it is difficult to grasp the deterioration state of the catalyst, the output signal of the oxygen sensor after the second control means executes at least one of the second to fourth controls, First determination means for executing control for determining whether or not the oxygen concentration of the gas in contact with the inner and outer surfaces of the detection element is an output signal indicating that the oxygen concentration in a normal oxygen sensor is reversed; When the first determination means determines that the oxygen concentration of the gas in contact with the inner and outer surfaces of the detection element is an output signal indicating that the oxygen concentration in the normal oxygen sensor is reversed, the first control is performed. The means may execute the first control. According to the present invention, when the maximum oxygen storage capacity of the catalyst described above becomes an abnormal value that is clearly different from, for example, a decrease due to deterioration of the catalyst, or data of the maximum oxygen storage capacity of the catalyst detected over time is obtained. Even when the battery disappears due to battery replacement or the like, it is possible to determine whether or not there is a possibility that an abnormality has occurred in the oxygen sensor by the first determination. Furthermore, when it is determined that an abnormality may have occurred, it is possible to execute the first control that can increase the detection accuracy of the abnormality diagnosis as compared with the second to fourth controls. . In addition, since the first control and the second, third, or fourth control are selectively used depending on whether it is difficult to grasp the deterioration state of the catalyst, the emission contained in the exhaust gas can be reduced, and the oxygen sensor malfunctions. Can be detected more suitably.

  In the present invention, the second control means detects an output signal of the oxygen sensor after the execution of at least one of the second to fourth controls over time, and the output detected over time. A second control for determining whether or not there is a predetermined number or more of output signals indicating that the oxygen concentration of the gas in contact with the inner and outer surfaces of the detection element is opposite to the oxygen concentration in a normal oxygen sensor. Having a determination means, and the second determination means has a predetermined number or more of output signals indicating that the oxygen concentration of the gas in contact with the inner and outer surfaces of the detection element is reversed from the oxygen concentration in a normal oxygen sensor. When the determination is made, the first control means may execute the first control. According to the present invention, in the output signal detected over time, for example, when a predetermined number or more of negative output signals satisfying a predetermined level are detected, there is a high possibility that an abnormality has occurred in the oxygen sensor. It can be said. In such a case, in the present invention, it is possible to improve the abnormality detection accuracy of the oxygen sensor by executing each diagnosis described above after further executing the first control. Further, as in the case where it is difficult to grasp the catalyst deterioration state, it is possible to detect the abnormality of the oxygen sensor more appropriately by properly using the first control and the second, third, or fourth control.

  ADVANTAGE OF THE INVENTION According to this invention, the abnormality detection apparatus of the oxygen sensor which detects abnormality more suitably can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram of an abnormality detection apparatus 100 according to the present invention. The abnormality detection device 100 includes an oxygen sensor 10, an ECU 50, and a memory (not shown) for storing detected output signals and the like. The ECU 50 includes first control means for executing first control, which will be described later in this embodiment, second control means for executing second control, and first to sixth for executing first to sixth diagnoses. It functions as a means. The oxygen sensor 10 includes a detection cover 1, a water repellent filter 3, a shield 4, an air hole 5, and a protective cover (not shown). The oxygen sensor 10 is disposed in the exhaust passage 2 in a state where the cup-shaped detection element 1 protrudes into the exhaust passage 2. A porous water-repellent filter 3 having excellent ventilation and water resistance is provided on the head of the oxygen sensor 10. The air flows into the detection element 1 through the water repellent filter 3 through the air holes 5 protruding from the shield 4 to the outside. On the other hand, the exhaust passage 2 is connected to an exhaust manifold (not shown), and exhaust gas is exhausted into the exhaust passage 2 from an internal combustion engine (not shown). The detection element 1 communicates with the atmosphere through the air hole 5 through the water repellent filter 3, but since the water repellent filter 3 plays a role of resistance, the gas from the detection element 1 through the atmosphere hole 5 Can be suppressed to some extent, and gas can be held in the detection element 1.

  FIG. 2 is a flowchart showing the control executed when the ECU 50 detects an abnormality of the oxygen sensor 10. In the abnormality detection device 100 in the present embodiment, the ECU 50 first determines whether or not a predetermined condition is satisfied (step 11). If the predetermined condition is not satisfied, the ECU 50 continues to execute step 11. The predetermined condition is, for example, the following condition. One of the predetermined conditions is, for example, whether or not the temperature of the detection element 1 of the oxygen sensor 10 has reached a predetermined temperature. This is because, when the temperature of the detection element 1 of the oxygen sensor 10 does not reach the predetermined temperature, a negative voltage may be generated even if the oxygen sensor 10 is normal. The reason why such a negative voltage is generated is that when the detection element 1 does not reach the predetermined temperature, the element resistance is large and the flow of oxygen ions in the detection element 1 becomes unstable. Therefore, for example, when it is determined by the impedance measurement of the oxygen sensor 10 or the engine water temperature measurement that the temperature of the detection element 1 has not reached the predetermined temperature, the abnormality of the oxygen sensor 10 is not detected until the temperature reaches the predetermined temperature.

  Yet another predetermined condition is, for example, whether the internal combustion engine is in a high-load operation state. This is because when the internal combustion engine is in a high-load operation state, a negative voltage may be generated similarly even if the oxygen sensor 10 is normal. The cause of such a negative voltage is that during high load operation, the internal combustion engine always exhausts exhaust gas under rich control, so oxygen ions flow from the atmosphere electrode inside the detection element 1 to the exhaust electrode outside the detection element 1. As a result, the inside of the detection element 1 is in an oxygen deficient state. Therefore, for example, when it is determined that the internal combustion engine is operating at a high load based on the intake air amount, the throttle opening, etc., when the high load operation has elapsed for a predetermined time, the oxygen sensor 10 is not detected for abnormality, The abnormality of the oxygen sensor 10 is not detected until a predetermined time has elapsed since the end of the high load operation. These predetermined conditions described above are not only applicable to the present embodiment, but are conditions that must be satisfied when an abnormality of the oxygen sensor 10 is detected. Further, the predetermined condition to be satisfied when the abnormality of the oxygen sensor 10 is detected is not limited to the above-described condition, and other conditions may be added so as not to misdiagnose that the normal oxygen sensor is abnormal. .

  When a predetermined condition is satisfied in step 11 of the flowchart shown in FIG. 2, the ECU 50 executes first control described later (step 12). After executing the first control, the ECU 50 executes any one of first to sixth diagnosis (hereinafter referred to as each diagnosis) to be described later, and determines whether there is an abnormality in the oxygen sensor 10 (step 13). . The above is the flow of the abnormality detection control of the oxygen sensor 10 executed by the ECU 50 according to the present embodiment.

  FIG. 3 is a diagram showing the output voltage 11a of the oxygen sensor 10 detected by the ECU 50 when the first control executed in step 12 of the flowchart shown in FIG. 2 is executed. FIG. 3 also shows the air-fuel ratio 14 of the air-fuel mixture burned by the internal combustion engine at the same time when the first control is executed. In FIG. 3, the vertical axis represents the output voltage 11a and the air-fuel ratio 14 of the oxygen sensor 10, and the horizontal axis represents time. In FIG. 3, a first threshold value 12 and a second threshold value 13 are set for the output voltage 11a. For example, when the output voltage 11a falls below the first threshold value 12 at the point 17a, the ECU 50 executes control to change the air-fuel ratio 14 to the first target value 15 in order to change the air-fuel ratio 14 to rich. Thus, when the air-fuel ratio 14 becomes rich, the oxygen concentration of the exhaust gas exhausted by the internal combustion engine decreases. That is, since the oxygen concentration of the gas outside the detection element 1 shown in FIG. 1 decreases, the oxygen partial pressure difference of the gas contacting the inner and outer surfaces of the detection element 1 increases, and the output voltage 11a gradually increases. Note that a certain time is required until the air-fuel ratio 14 is changed to the first target value 15, and a certain time is required until the exhaust gas reaches the exhaust passage 2 in which the oxygen sensor 10 is disposed. Cost. Therefore, even after the control for changing the air-fuel ratio 14 to the first target value 15 is executed at the time of the point 17a, the output voltage 11a decreases until then.

  When the output voltage 11a rises and exceeds the second threshold value 13 at the point 17b, the ECU 50 executes control to change the air-fuel ratio 14 to the second target value 16 in order to change the air-fuel ratio 14 to lean. To do. Thereby, when the air-fuel ratio 14 becomes lean, the oxygen concentration of the exhaust gas exhausted by the internal combustion engine increases. That is, since the oxygen concentration of the gas outside the detection element 1 of the oxygen sensor 10 shown in FIG. 1 increases, the oxygen partial pressure difference of the gas contacting the inner and outer surfaces of the detection element 1 decreases, and the output voltage 11a gradually decreases. For the same reason as described above, the output voltage 11a rises for a while even after the control for changing the air-fuel ratio 14 to the second target value 16 is executed at the time of the point 17b. After the first control is executed, the ECU 50 changes the air-fuel ratio 14 to the first target value 15 when the output voltage 11a falls below the first threshold value 12, and the output voltage 11b changes the second threshold value 13 to the first threshold value 12. If it exceeds, the control to change the air-fuel ratio 14 to the second target value 16 is repeatedly executed until a predetermined time elapses. Thus, the 1st control which ECU50 of abnormality detection device 100 performs can be realized.

  When the detection element 1 has a defect 6 as shown in FIG. 1 when the first control described above is executed, the exhaust gas generated by repeatedly changing the air-fuel ratio 14 to lean or rich is shown. The exhaust gas gradually enters the detection element 1 due to periodic pressure fluctuations. When exhaust gas enters the detection element 1, the oxygen concentration in the detection element 1 gradually decreases. For example, when the oxygen concentration of the gas outside the detection element 1 is the same and the gas concentration inside the detection element 1 is higher than the gas concentration outside the detection element 1, the oxygen concentration of the gas inside the detection element 1 decreases. Then, the oxygen partial pressure difference between the gas inside and outside the detection element 1 becomes small. That is, when the exhaust gas enters through the defect 6, the output voltage 11a of the oxygen sensor 10 decreases. As a result, when the exhaust gas gradually enters the detection element 1, the upper peak value 18 of the output voltage 11a gradually decreases to 18a, 18b, and 18c. Similarly, the lower peak value 19 of the output voltage 11a gradually decreases to 19a, 19b, and 19c. The reason why the lower peak value 19c of the output voltage 11a does not fall below zero is that in the present embodiment, the ECU 50 incorporates a detection circuit capable of detecting only a positive voltage. Therefore, in this state, the oxygen concentration of the gas inside and outside the detection element 1 is actually reversed from the oxygen concentration in a normal oxygen sensor.

  In the present embodiment, the following first diagnosis is executed based on the output voltage 11a detected in this way. The upper peak value 18 of the output voltage 11a is detected, and it is determined whether or not the difference 18d between the adjacent upper peak values 18a and 18b of the output voltage 11a is greater than or equal to a predetermined value. Further, it is determined whether or not the difference 18e between the adjacent upper peak values 18b and 18c of the output voltage 11a is equal to or greater than a predetermined value. When these differences 18d and 18e are equal to or greater than a predetermined value and are continuously detected a predetermined number of times, the ECU 50 diagnoses that there is an abnormality. As described above, in the first diagnosis, since the determination is made by capturing the phenomenon that the output voltage 11a decreases with time, for example, when abnormality is diagnosed based on the output signal of the oxygen sensor 10 detected alone at a certain moment (hereinafter, referred to as “the first diagnosis”) Compared with normal abnormality diagnosis), the abnormality of the oxygen sensor 10 can be detected stably and reliably.

  Since the upper peak value 18 gradually decreases, the presence or absence of abnormality of the oxygen sensor 10 can be diagnosed even with other parameters having a correlation with the change of the upper peak value 18. For example, it is possible to diagnose that there is an abnormality when the slope of the straight line as shown by the straight line 25 connecting the adjacent upper peak values 18a and 18b becomes a predetermined value or more continuously for a predetermined number of times. Further, the difference between the two upper peak values 18 may not be adjacent to each other. In the output voltage 11a shown in FIG. 3, for example, the upper peak value 18b is skipped, and the difference between the upper peak values 18a and 18c is a predetermined value. It is also possible to determine whether or not this is the case. Further, instead of detecting the above-described upper peak value 18, the lower peak value 19 may be detected, and a determination similar to the above-described determination may be performed to diagnose whether the oxygen sensor 10 is abnormal.

  Next, the first control described above executed in step 12 of the flowchart shown in FIG. 2 will be described in detail based on the output voltage 11a shown in FIG. FIG. 4 is a flowchart showing the first control. After starting execution of the first control, the ECU 50 determines whether or not the output voltage 11a exceeds the second threshold value 13 (step 21). If so, the ECU 50 executes step 26. If not, the ECU 50 determines whether or not the output voltage 11a is below the first threshold value 12 (step 22). If it falls below, the ECU 50 executes step 24. If not, the ECU 50 executes step 21 again. That is, in a state where it is unknown whether the output voltage 11a is increasing or decreasing, in step 21 and step 22, the ECU 50 determines whether the output voltage 11a passes the first threshold value 12 or the second threshold value 13. judge.

  When the output voltage 11a falls below the first threshold value 12 in step 22, the ECU 50 changes the air-fuel ratio 14 to the first target value 15 (step 24). Subsequently, the ECU 50 determines whether or not the output voltage 11a exceeds the second threshold value 13 (step 25). If not, the ECU 50 executes step 27. If it exceeds, the ECU 50 changes the air-fuel ratio 14 to the second target value 16 (step 26). Even in the case where the output voltage 11a exceeds the second threshold value 13 in step 21 described above, step 26 is similarly executed. Subsequently, the ECU 50 determines whether or not a predetermined time has elapsed (step 28). The predetermined time is, for example, the time until the end of the first control set with the start of the first control execution as the start. When the predetermined time has elapsed, the ECU 50 ends the first control, and when the predetermined time has not elapsed, the ECU 50 executes Step 23 again. When the output voltage 11a does not exceed the second threshold 13 in step 25, the ECU 50 determines whether a predetermined time has elapsed (step 27). This predetermined time may be, for example, the time until the end of the first control set when the output voltage 11a falls below the first threshold value 12, and the first control is executed as in step 28. It may be a time starting from the start time. If the predetermined time has not elapsed, the ECU 50 executes Step 25 again, and if the predetermined time has elapsed, the ECU 50 ends the first control. Thus, the first control executed by the ECU 50 of the abnormality detection device 100 can be realized.

  Next, the above-described first diagnosis executed in step 13 of the flowchart shown in FIG. 2 will be described in detail with reference to the flowchart based on the output voltage 11a shown in FIG. FIG. 5 is a flowchart showing the first diagnosis. It should be noted that the second to sixth diagnosis flowcharts to be described later are omitted by illustrating the first diagnosis flowchart shown in FIG. 5 as a representative example. After executing the first control in step 12 of the flowchart shown in FIG. 2, the ECU 50 executes the first diagnosis in step 13. After starting the execution of the first diagnosis, the ECU 50 detects the upper peak value 18 of the output voltage 11a (step 31). Subsequently, the ECU 50 determines whether or not the difference 18d between the adjacent upper peak values 18a and 18b is equal to or greater than a predetermined value (step 32). If it is smaller than the predetermined value, the ECU 50 determines in step 35 that the oxygen sensor 10 is normal. If it is equal to or greater than the predetermined value, the ECU 50 subsequently determines whether or not the difference 18e between the adjacent upper peak values 18b and 18c is equal to or greater than the predetermined value (step 33). If it is smaller than the predetermined value, the ECU 50 determines in step 35 that the oxygen sensor 10 is normal, as in step 32. If it is equal to or greater than the predetermined value, the ECU 50 determines whether or not the differences 18d and 18e between the adjacent upper peak values 18 have been detected a predetermined number of times (step 34). If the predetermined number of times is not detected, the ECU 50 determines in step 35 that the oxygen sensor 10 is normal, as in steps 32 and 33 described above. If it is detected a predetermined number of times, the ECU 50 determines that a defect 6 has occurred in the detection element 1 of the oxygen sensor 10 (step 36). As described above, the first diagnosis executed by the ECU 50 of the abnormality diagnosis apparatus 100 can be realized.

  In addition, based on the output voltage 11a shown in FIG. 3, the second diagnosis can be executed in step 13 of the flowchart shown in FIG. The decrease in the output voltage 11 a shown in FIG. 3 when the defect 6 occurs in the detection element 1 can also be regarded as a decrease in the amplitude 20. In the second diagnosis, this amplitude 20 is detected, and it is determined whether or not the difference between the adjacent amplitudes 20a and 20b is greater than or equal to a predetermined value. Further, it is determined whether or not the difference between adjacent amplitudes 20b and 20c is equal to or greater than a predetermined value. When these differences are equal to or greater than a predetermined value and are continuously detected a predetermined number of times, the ECU 50 diagnoses that the oxygen sensor 10 is abnormal. Also by this second diagnosis, since the determination is made by catching the phenomenon that the output voltage 11a decreases with time, a more preferable abnormality detection of the oxygen sensor 10 can be realized. Since the amplitude 20 gradually decreases, the abnormality of the oxygen sensor 10 can be diagnosed even with other parameters having a correlation with the change of the amplitude 20. For example, it is possible to diagnose that there is an abnormality when the apparent power, which is the product of the effective value of the current and the effective value of the voltage, continuously decreases a predetermined value or more a plurality of times. Further, as in the case of the first diagnosis, the determination may not be made based on the difference between the adjacent amplitudes 20.

  Moreover, based on the output voltage 11a shown in FIG. 3, it is also possible to detect the abnormality of the oxygen sensor 10 by executing the third diagnosis in step 13 of the flowchart shown in FIG. As described above, when the detection circuit capable of detecting only the positive voltage is incorporated in the ECU 50, the output voltage 11a does not become lower than 0V even if the defect 6 occurs in the detection element 1. That is, the presence or absence of abnormality of the oxygen sensor 10 can be diagnosed by detecting the lower peak value 19 of the output voltage 11a and determining whether or not it is continuously 0V for a predetermined number of times.

  Further, based on the output voltage 11 of the oxygen sensor 10 when the first control is executed, a fourth diagnosis as shown below can be executed to detect an abnormality. FIG. 6 is a diagram showing the output signal 11b of the oxygen sensor 10 detected by the ECU 50 of the abnormality detection device 100 according to the present invention when the first control is executed in step 12 of the flowchart shown in FIG. In FIG. 6, the vertical axis indicates the output voltage of the oxygen sensor 10, and the horizontal axis indicates time. When the oxygen sensor 10 has a defect 6, a negative detection voltage 21 a and 21 b as shown in part A of the output voltage 11 b when the first control is executed by incorporating a detection circuit capable of detecting a negative voltage into the ECU 50. Can be detected. Such negative voltages 21a and 21b are generated when the exhaust gas that has entered the detection element 1 includes exhaust gas exhausted by rich control. That is, when exhaust gas exhausted by rich control enters the detection element 1 through the defect 6, depending on the amount of exhaust gas that has entered, the oxygen concentration of the gas in the detection element 1 is exhaust gas exhausted by lean control. Lower than. Therefore, when the exhaust gas is subsequently exhausted by lean control, the oxygen concentration of the gas inside the detection element 1 becomes lower than the oxygen concentration of the gas outside the detection element 1. That is, the oxygen concentration of the gas inside and outside the detection element 1 is reversed from the oxygen concentration in the normal oxygen sensor 10, and as a result, negative voltages 21 a and 21 b are generated in the oxygen sensor 10. Thus, even if the lower peak value 19 of the output voltage 11b is detected and it is determined whether a negative voltage is continuously generated a predetermined number of times, it is possible to diagnose whether the oxygen sensor 10 is abnormal.

  Further, based on the output voltage 11b shown in FIG. 6, a fifth diagnosis can be further executed to detect abnormality of the oxygen sensor 10. When the defect 6 occurs in the detection element 1 of the oxygen sensor 10 when the first control is executed, the upper peak value 22 of the output voltage 11b gradually decreases to 22a, 22b, and 22c. Further, when the upper peak value 22 of the output voltage 11b decreases and becomes the upper peak value 22d, the output voltage 11b cannot exceed the second threshold value 13. In such a case, the feedback control (also referred to as FB) of the air-fuel ratio 14 shown in FIG. 3 realized by the first control is not established, so the first control is stopped. Whether or not the first control stop occurs within a predetermined time, that is, whether or not the FB impossible arrival time 23 from the start of the first control execution until the upper peak value 22d of the output voltage 11b is detected is within the predetermined time. Even if it is determined, it is possible to diagnose whether the oxygen sensor 10 is abnormal. In this case, if the FB impossible arrival time 23 is within a predetermined time, it is diagnosed that there is an abnormality. It is also possible to diagnose whether or not the oxygen sensor 10 is abnormal by determining whether the air-fuel ratio 14 has been changed to rich or lean within a predetermined time by a predetermined number of times. In this case, if the number of times the air-fuel ratio 14 is changed to rich or lean is equal to or less than the predetermined number, it is diagnosed that there is an abnormality. Note that the ECU 50 may function as a diagnostic unit that executes all the first to sixth diagnoses described above, and may select a diagnosis to be executed according to a predetermined condition from each diagnosis. Moreover, each diagnosis may be executed in combination with the output voltage 11 detected as a result of executing the first control, or one diagnosis is executed from the above-described diagnoses, and the first control is performed again. It is also possible to execute another diagnosis after executing.

FIG. 7 is a schematic diagram showing another embodiment of the abnormality detection apparatus 100 according to the present invention. Further, in the present embodiment, the point that the oxygen sensor 10 is disposed in the exhaust passage 2 on the downstream side of the catalyst 30 is different from that in the first embodiment, and the ECU 50 in addition to the means described in the first embodiment, Except for functioning as first determination means for executing first determination described later, the configuration is the same as that of the abnormality detection apparatus 100 shown in FIG. However, the oxygen sensor 10 may be disposed, for example, at a position indicated by part B of the catalyst 30. The catalyst 30 is configured to oxidize emissions contained in exhaust gas, that is, to oxidize CO and HC to harmless CO ₂ and H ₂ O, or to reduce NOx to N ₂ and O ₂ . The exhaust gas is exhausted from an internal combustion engine (not shown) and reaches the exhaust passage 2 through the catalyst 30. Although the catalyst 30 gradually deteriorates with use, when the catalyst 30 has not deteriorated, the maximum oxygen storage capacity of the catalyst 30 is higher than that after deterioration. Since the catalyst 30 occludes oxygen, an exhaust gas having a lower oxygen concentration flows in the exhaust passage 2 on the downstream side of the catalyst 30 than in the upstream exhaust passage 2 (not shown) of the catalyst 30. Therefore, when the defect 6 is generated in the detection element 1, such an exhaust gas having a low oxygen concentration enters through the defect 6. In this situation, for example, after executing the second control for executing fuel cut in the internal combustion engine or the third control for changing the air-fuel ratio 14 to be leaner than the stoichiometric air-fuel ratio, the above-described normal abnormality diagnosis is executed. Thus, a sufficiently detectable oxygen concentration difference can be generated in the gas inside and outside the detection element 1. In other words, in a situation where the catalyst 30 has not deteriorated, the reliability is determined by the second control or the third control and the normal abnormality diagnosis without executing the first control and each diagnosis detailed in the first embodiment. It can be said that a high result is obtained. Note that the fourth control for changing the air-fuel ratio 14 to be richer than the stoichiometric air-fuel ratio may be executed before executing the second control or the third control. In this case, the exhaust gas having a lower oxygen concentration can be introduced into the detection element 1 in advance through the defect 6 before the normal abnormality diagnosis is performed.

  On the other hand, when the catalyst 30 deteriorates, the maximum oxygen storage capacity of the catalyst 30 also decreases. Therefore, the oxygen concentration of the exhaust gas that passes through the catalyst 30 and flows into the exhaust passage 2 becomes higher than the oxygen concentration before the catalyst 30 deteriorates. Therefore, when the defect 6 is generated in the detection element 1, the exhaust gas having a higher oxygen concentration enters through the defect 6 as compared with the case where the catalyst is not deteriorated. In such a situation, depending on the degree of deterioration of the catalyst, even if the normal abnormality diagnosis is executed after executing the second control or the third control, the detection element 1 of the oxygen sensor 10 has a defect 6. When this occurs, there is a possibility that a sufficiently detectable oxygen concentration difference cannot be generated in the gas inside and outside the detection element 1. Even when the fourth control for changing the air-fuel ratio 14 to be richer than the stoichiometric air-fuel ratio is executed before the second control or the third control is executed, there is still a difference in degree, but the catalyst 30 is still used. The same can be said depending on the degree of deterioration. That is, when the catalyst 30 is deteriorated, it is difficult to detect an abnormality of the oxygen sensor 10 based on a normal abnormality diagnosis.

  In this embodiment, in this embodiment, the maximum oxygen storage capacity of the catalyst 30 is measured over time, for example, every time the internal combustion engine is started, and when the maximum oxygen storage capacity is lower than a predetermined value, that is, the catalyst 30 When it is determined that the sensor is deteriorated, the abnormality of the oxygen sensor 10 can be stably detected by executing the first control and each diagnosis detailed in the first embodiment. That is, when a normal abnormality diagnosis is executed, even if it is difficult to detect an abnormality of the oxygen sensor 10 as described above, the first embodiment is based on the output voltage 11 of the oxygen sensor 10 when the first control is executed. If each diagnosis detailed in the above is executed, it is possible to diagnose that there is an abnormality by capturing the phenomenon that the output voltage 11 gradually decreases. Further, by properly using the first control and the second control or the third control before and after deterioration of the catalyst 30, the abnormality of the oxygen sensor 10 can be detected more suitably. That is, when the second control or the third control and the normal diagnosis are executed without executing the first control and each diagnosis detailed in the first embodiment, the emission contained in the exhaust gas is reduced. There are advantages such as being able to. Note that the time-dependent measurement of the maximum oxygen storage capacity does not have to be performed every time the internal combustion engine is started. For example, it is sufficient if a calendar timer or the like is provided to measure the deterioration of the catalyst 30 at regular intervals.

  Further, in this embodiment, when it is difficult to grasp the deterioration state of the catalyst 30, it is possible to detect an abnormality of the oxygen sensor 10 by executing the first determination as described below. As described above, when the maximum oxygen storage capacity of the catalyst 30 is measured over time, for example, when a sudden decrease in the oxygen storage capacity that is clearly different from the decrease due to a change with time is detected, the value of this maximum oxygen storage capacity is detected. Is not reliable. Therefore, in this embodiment, when the oxygen storage capacity indicating such a rapid decrease is detected, the first control is not executed, and the second control or the third control is executed first. Thereafter, a normal abnormality diagnosis is executed, and an output signal indicating that the oxygen concentration of the gas inside and outside the detection element 1 is reversed from the oxygen concentration in the normal oxygen sensor 10, that is, in this embodiment, the negative voltage is at a predetermined level. When it determines with having detected above, the 1st control and each diagnosis which were explained in full detail in Example 1 are performed. As described above, by properly using the first control and the second control or the third control, it is possible to detect the abnormality of the oxygen sensor 10 more suitably. In order to detect whether or not there is a possibility that an abnormality has occurred in the oxygen sensor 10, for example, the predetermined level described above is set to a voltage level that determines that a negative voltage is generated in a normal abnormality diagnosis. If it is, it may be set lower than this voltage level. In addition, it is naturally possible to diagnose that the oxygen sensor may be abnormal when a negative voltage is detected without setting the voltage level. Moreover, you may perform 4th control before performing 2nd or 3rd control.

  In addition, when a battery used as a power supply source for various sensors, electronic devices, ECU 50, or the like is replaced or when a terminal of the battery is removed, the catalyst 30 measured and stored in the memory before the battery is replaced. The maximum oxygen storage capacity data may disappear. In such a case, it becomes impossible to compare the maximum oxygen storage capacity of the catalyst 30 measured over time before battery replacement or the like with the maximum oxygen storage capacity measured after battery replacement. In such a situation, in the present embodiment, when battery replacement or the like is performed, the second control or the third control is first executed as in the case described above. Thereafter, a normal abnormality diagnosis is executed, and an output signal indicating that the oxygen concentration of the gas inside and outside the detection element 1 is reversed from the oxygen concentration in the normal oxygen sensor 10, that is, in this embodiment, the negative voltage is at a predetermined level. When it determines with having detected above, the 1st control and each diagnosis which were explained in full detail in Example 1 are performed. When the oxygen sensor 10 is diagnosed as a result of executing the second control or the third control and the normal abnormality diagnosis after the battery replacement or the like, the maximum oxygen storage capacity of the catalyst 30 is continuously changed over time. Will be measured. Note that the predetermined level described above may be set lower than this voltage level when a voltage level is determined to determine that a negative voltage has occurred in normal abnormality diagnosis. It is naturally possible to diagnose that the oxygen sensor is abnormal when a negative voltage is detected without setting the voltage level. Further, the fourth control may be executed before the second or third control is executed.

  Next, the control executed when the ECU 50 detects an abnormality of the oxygen sensor 10 in the situation where the deterioration state of the catalyst 30 becomes difficult to grasp will be described in detail. FIG. 8 is a flowchart showing a control including a first determination executed when the ECU 50 detects an abnormality of the oxygen sensor 10 in a situation where it is difficult to grasp the deterioration state of the catalyst 30. In the flowchart shown in FIG. 8, a step indicated by a double line is a step related to the first determination. The ECU 50 executes the first determination control using, for example, the start of the internal combustion engine as a trigger (step 41). Subsequently, when executing the abnormality detection of the oxygen sensor 10, the ECU 50 determines whether or not a predetermined condition is satisfied as in the case described above in the first embodiment (step 42). If the predetermined condition is not satisfied, the ECU 50 executes step 42 repeatedly. If the predetermined condition is satisfied, the ECU 50 determines whether there is data on the maximum oxygen storage capacity of the catalyst 30 stored in the memory (step 43). If there is no data, the ECU 50 executes step 51. If the data exists, the ECU 50 determines whether or not the maximum oxygen storage capacity stored in the memory is equal to or less than a predetermined value (step 44). If it is greater than the predetermined value, the ECU 50 executes step 46. If it is less than or equal to the predetermined value, the ECU 50 determines whether or not the maximum oxygen storage capacity has suddenly decreased (step 45). In addition, even when the maximum oxygen storage capacity is suddenly decreased, when it becomes difficult to grasp the maximum oxygen storage capacity, it is possible to execute an appropriate determination in this step. If it is determined that the battery has suddenly decreased, the ECU 50 executes step 51 as in step 43. If it is determined that it is not a sudden drop, the ECU 50 executes the first control (step 55). Subsequently, the ECU 50 executes each diagnosis detailed in the first embodiment, and determines whether or not the oxygen sensor 10 is abnormal (step 56).

  Further, when step 51 is to be executed in step 43 or step 45, the ECU 50 executes the second or third control without executing the first control. Subsequently, the ECU 50 performs normal abnormality diagnosis (step 52), and determines whether or not a negative voltage of a predetermined level or higher is generated from the oxygen sensor 10 (step 53). When a negative voltage of a predetermined level or higher is generated, it is estimated that there is a high possibility that an abnormality has occurred in the oxygen sensor 10, and the ECU 50 executes the first control in step 55. If a negative voltage of a predetermined level or higher is not generated, it is determined that the oxygen sensor 10 is normal (step 54), and the abnormality detection of the oxygen sensor 10 is terminated. On the other hand, if it is determined in step 44 that the maximum oxygen storage capacity is greater than the predetermined value, the ECU 50 executes second or third control in step 46 (step 46). Subsequently, the ECU 50 performs normal abnormality diagnosis (step 47), and determines whether or not a negative voltage is generated from the oxygen sensor 10 (step 48). If the negative voltage is not generated, the ECU 50 determines that the oxygen sensor 10 is normal (step 49). If the negative voltage is generated, the ECU 50 determines that the oxygen sensor 10 is abnormal (step 50). . As described above, when the deterioration state of the catalyst 30 is difficult to grasp, it is possible to detect the abnormality of the oxygen sensor 10 more suitably by properly using the first control, the second control, or the third control.

  The configuration of the abnormality detection apparatus 100 according to the present embodiment is shown in FIG. 1 except that the ECU 50 functions as a second determination means for executing a second determination described later in addition to the means described in the second embodiment. The configuration is the same as that of the abnormality detection apparatus 100. Further, the arrangement position of the oxygen sensor 10 in the exhaust passage 2 is not limited to the downstream side of the catalyst 30 as in the second embodiment.

  In this embodiment, after the second control or the third control described above is executed, the output voltage of the oxygen sensor 10 is detected independently at a certain moment as in a normal abnormality diagnosis. Further, the detection of the output voltage is performed with time, for example, every time the internal combustion engine is started. In addition, it does not restrict | limit detecting the output voltage of the oxygen sensor 10 continuously. Further, the control for detecting the output voltage with time may not be performed every time the internal combustion engine is started.

  After executing the control for detecting the output voltage over time, in this embodiment, it is further determined whether or not the detected plurality of output voltages satisfy a predetermined condition shown below. That is, it is determined whether, for example, a negative voltage having a predetermined level or more exists more than a predetermined number of times in the detected plurality of output voltages. If it is determined that such a condition is satisfied, it can be said that there is a possibility that an abnormality has occurred in the oxygen sensor 10. After the determination, if the first control and each diagnosis detailed in the first embodiment are executed, it is possible to detect the presence or absence of abnormality of the oxygen sensor 10 more suitably. That is, normally, for example, every time the internal combustion engine is started, the second or third control is executed and then the output voltage is detected to determine whether or not there is a possibility that an abnormality has occurred in the oxygen sensor 10. Thereafter, only after it is determined that there is a possibility that an abnormality has occurred, the first control and each diagnosis are executed. Therefore, it is possible to reduce emissions contained in the exhaust gas. Note that the fourth control may be executed before the second or third control described above is executed.

  Next, the control executed when the ECU 50 detects the abnormality of the oxygen sensor 10 in the above-described situation will be described in detail with reference to FIG. FIG. 9 is a flowchart showing a control including a second determination executed when the ECU 50 detects an abnormality of the oxygen sensor 10. In the flowchart shown in FIG. 9, a step indicated by a double line is a step related to the second determination. The ECU 50 executes the second determination according to the present embodiment using, for example, the start of the internal combustion engine as a trigger (step 61). Subsequently, the ECU 50 determines whether or not the predetermined condition described in the first embodiment is satisfied (step 62). If the predetermined condition is not satisfied, the ECU 50 continues to execute step 62. If the predetermined condition is satisfied, the ECU 50 detects the output voltage of the oxygen sensor 10 (step 63). Subsequently, the ECU 50 determines whether a predetermined number or more of negative voltages of a predetermined level or higher have been detected (step 64). If step 64 is not satisfied, the ECU 50 determines that the oxygen sensor 10 is normal (step 65). If step 64 is satisfied, the ECU 50 executes the first control (step 66). Subsequently, the ECU 50 executes each diagnosis and determines whether or not the oxygen sensor 10 is abnormal (step 67). As described above, the abnormality detection that executes the first control and each diagnosis can be realized only after it is determined that an abnormality may have occurred based on the output voltage detected over time.

  It should be noted that the predetermined value, the predetermined time, the predetermined number of times, the predetermined level of the negative voltage, and the like at the time of determination in each of the above-described embodiments are obtained by optimum values by, for example, experiments, etc. It may be set as appropriate depending on the installation position, the internal combustion engine to be applied, the operating conditions of the internal combustion engine, and the like. As described above, the abnormality detection apparatus 100 that detects an abnormality of the oxygen sensor 10 more appropriately can be realized.

  The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

1 is a schematic diagram of an abnormality detection apparatus 100 according to the present invention. It is a figure which shows the control performed when ECU50 detects the abnormality of the oxygen sensor 10 with a flowchart. It is a figure which shows the output voltage 11a of the oxygen sensor 10 which ECU50 detected. It is a figure which shows 1st control with a flowchart. It is a figure which shows a 1st diagnosis with a flowchart. It is a figure which shows the output signal 11b of the oxygen sensor 10 which ECU50 detected. It is a schematic diagram which shows the other Example of the abnormality detection apparatus 100 which concerns on this invention. It is a figure which shows the control including the 1st determination performed when ECU50 performs abnormality detection of the oxygen sensor 10 with a flowchart. It is a figure which shows the control including the 2nd determination performed when ECU50 performs abnormality detection of the oxygen sensor 10 with a flowchart. It is the figure which showed the detection element part in a common oxygen sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Detection element 2 Exhaust passage 3 Water repellent filter 4 Shield 5 Atmospheric hole 6 Deletion 10 Oxygen sensor 11a, 11b Output signal 12 1st threshold value 13 2nd threshold value 14 Air fuel ratio 15 1st target value 16 2nd target value 17a, 17b Point 18 Upper peak value of the output voltage 11a 19 Lower peak value of the output voltage 11a 20 Amplitude of the output voltage 11a 21a, 21b Negative voltage 22 Upper peak value of the output voltage 11b 23 FB impossible arrival time 25 Connect the upper peak value Straight line 30 Catalyst 50 ECU
100 Abnormality detection device

Claims (12)

Anomaly detection of an oxygen sensor provided with a detection element that is arranged between the first gas and the second gas and generates an electromotive force according to an oxygen partial pressure difference between the first gas and the second gas A device,
The second gas is an exhaust gas that is exhausted when the internal combustion engine burns the air-fuel mixture at a predetermined air-fuel ratio,
Diagnostic means for executing control for diagnosing the presence or absence of abnormality of the oxygen sensor;
Before the diagnosis means performs control for diagnosing the presence or absence of abnormality of the oxygen sensor, the first output signal of the oxygen sensor when the threshold value set for the output signal of the oxygen sensor is passed. And an oxygen sensor abnormality detection device comprising: first control means for executing first control for changing the air-fuel ratio of the air-fuel mixture to leaner or richer than the stoichiometric air-fuel ratio. The diagnostic means executes control for diagnosing the presence or absence of abnormality of the oxygen sensor based on the second output signal of the oxygen sensor when the first control means executes the first control. The oxygen sensor abnormality detection device according to claim 1, wherein: 3. The control for diagnosing that there is an abnormality by detecting that the peak value of the second output signal has changed a predetermined value or more continuously for a predetermined number of times. Oxygen sensor abnormality detection device. 3. The control according to claim 2, wherein the diagnosis unit executes control for diagnosing that there is an abnormality by detecting that the amplitude of the second output signal continuously changes a predetermined value or more for a predetermined number of times. Oxygen sensor abnormality detection device. 3. The control according to claim 2, wherein the diagnosis unit executes control for diagnosing that there is an abnormality by detecting that the peak value of the second output signal is continuously zero for a predetermined number of times. Oxygen sensor abnormality detection device. The diagnostic means indicates that the peak value of the second output signal continues for a predetermined number of times, and the oxygen concentration of the gas contacting the inner and outer surfaces of the detection element is reversed from the oxygen concentration in a normal oxygen sensor. 3. The oxygen sensor abnormality detection device according to claim 2, wherein control for diagnosing that there is an abnormality by detecting that the output signal has been performed is executed. When the first control is stopped due to the second output signal of the oxygen sensor not passing through the threshold value, the diagnosis means stops the first control within a predetermined time. The oxygen sensor abnormality detection device according to claim 2, wherein control for diagnosing that there is an abnormality by detecting occurrence of the abnormality is executed. The diagnostic means detects that the number of times the first control means has changed the air / fuel ratio to be richer or leaner than the stoichiometric air / fuel ratio is less than or equal to a predetermined number of times within a predetermined time and diagnoses that there is an abnormality. The oxygen sensor abnormality detection device according to claim 2, wherein control is executed. A second control for performing fuel cut in the internal combustion engine;
A third control for changing the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio;
Before executing the second control or before executing the third control, execute at least one of the fourth control for changing the air-fuel ratio to be richer than the stoichiometric air-fuel ratio. Having control means,
Diagnostic means for executing control for diagnosing the presence or absence of abnormality of the oxygen sensor based on an output signal of the oxygen sensor after the second control means executes at least one of the second to fourth controls; The oxygen sensor abnormality detection device according to any one of claims 1 to 8, further comprising: In the exhaust passage where the oxygen sensor is connected to the internal combustion engine, disposed on the downstream side of the catalyst provided in the exhaust passage,
The oxygen sensor abnormality detection device according to claim 9, wherein the first control unit executes the first control when the catalyst is deteriorated. When the deterioration state of the catalyst is difficult to grasp, the output signal of the oxygen sensor after the second control means executes at least one of the second to fourth controls is output to the inner and outer surfaces of the detection element. First determining means for executing control for determining whether or not the oxygen concentration of the gas in contact is an output signal indicating that the oxygen concentration in the normal oxygen sensor is reversed;
When the first determination means determines that the oxygen concentration of the gas contacting the inner and outer surfaces of the detection element is an output signal indicating that the oxygen concentration in the normal oxygen sensor is reversed, the first determination means The oxygen sensor abnormality detection device according to claim 10, wherein a control unit executes the first control. The output signal of the oxygen sensor after the second control means executes at least one of the second to fourth controls is detected over time, and in the output signal detected over time, the detection element There is a second determination means for executing control for determining whether or not there is a predetermined number or more of output signals indicating that the oxygen concentration of the gas in contact with the inner and outer surfaces is opposite to the oxygen concentration in a normal oxygen sensor. And
When the second determination means determines that there is a predetermined number or more of output signals indicating that the oxygen concentration of the gas in contact with the inner and outer surfaces of the detection element is reversed from the oxygen concentration in a normal oxygen sensor, The oxygen sensor abnormality detection device according to claim 9, wherein the first control unit executes the first control.

Images